Method and composition for stabilizing incompetent sand containing forma-tions

ABSTRACT

COMPOSITION AND METHOD OF TREATING AN OIL-CONTAINING INCOMPETENT FORMATION TO PREVENT THE MOVEMENT OF UNCONSOLIDATED SAND PARTICLES IN A WELL BORE BY FORMING A (SLURRY) TREATING COMPOSITION OF SAN, CEMENT AND A SUFFICIENT AMOUNT OF A PETROLEUM OIL FRACTION CONTAINING AN OIL WETTING AGENT THEREIN TO OIL WET THE SAND AND CEMENT PARTICLES, SUSPENDING THE (OIL WET SAND AND CEMENT PARTICLES) FORMED TREATING COMPOSITION IN AN AQUEOUS CARRIER MEDIUM, INJECTING THE AQUEOUS SUSPENSION AGAINST THE UNCONSOLIDATED FORMATION AT A PRESSURE EFFECTIVE TO FORCE THE (SUSPENSION) TREATING COMPOSITION INTO CONTACT WITH THE UNCONSOLIDATED FORMATION, CONTACTING THE PLACED TREATING COMPOSITION (SUSPENSION) WITH AN AQUEOUS SURFACE ACTIVE AGENT SOLUTION TO WATER WET THE CEMENT PARTICLES, PERMITTING THE CEMENT TO SET AND FORM A PERMEABLE CEMENT AND RECOVERING OIL THROUGH THE CEMENT.

United States Patent METHOD AND COMPOSITION FOR STABILIZING ggggdPE'l'ENT SAND CONTAINING FORMA- Bobby G. Harnsberger and Joy T. Payton, Houston, Tex.,

assignors to Texaco Inc., New York, N.Y.

No Drawing. Original No. 3,429,373, dated Feb. 25, 1969, Ser. No. 723,935, Apr. 24, 1968. Application for reissue Feb. 25, 1970, Ser. No. 14,250

Int. Cl. C04b 7/00; E2lb 33/13, 43/02 US. Cl. 166-276 22 Claims Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE Composition and method of treating an oil-containing incompetent formation to prevent the movement of unconsolidated sand particles in a well bore by forming a [slurry] treating composition of sand, cement and a sufficient amount of a petroleum oil fraction containing an oil wetting agent therein to oil wet the sand and cement particles, suspending the [oil wet sand and cement particles] formed treating composition in an aqueous carrier medium, injecting the aqueous suspension against the unconsolidated formation at a pressure effective to force the [suspension] treating composition into contact with the unconsolidated formation, contacting the placed treating composition [suspension] with an aqueous surface active agent solution to water wet the cement particles, permitting the cement to set and form a permeable cement and recovering oil through the cement.

This is a C-l-P application of application Ser. No. 597,532, filed Nov. 29, 1966, now abandoned.

The present invention relates to the treatment of permeable underground formations. More particularly, the present invention relates to a method of treating permeable underground oil and/or gas containing formations to stabilize the sandy portion thereof and to a treating composition useful in the stabilization of incompetent sand containing underground formations.

The recovery of fluids such as gas and/or oil from underground formations has been troublesome in areas wherein the underground formation is composed of one or more incompetent sand containing layers or zones. The sand particles in the incompetent zone and/or layer tend to move or migrate to the well bore during recovery of the formation fluids from the particular zone and/or layer and frequently the moving sand particles block the passageways leading to the well bore. Plugging or materially impairing the flow of the formation fluids toward the bore hole results in a loss of these fluids to the producer or so decreases the rate of oil recovery from the 'well as to cause the well to be shut down because it is economically unattractive to continue to produce therefrom. An additional adverse factor resulting from the movement of the sand particles toward the well bore is that they are often carried along with the formation fluids to the well bore and passed through the pipes, pumps, etc. being used to recover the formation fluids to the surface with resulting damage to the moving parts thereof as the sand particles are very abrasive.

Many attempts have been made heretofore to prevent or decrease the flow of undesirable sand particles in the formation and/or in the production tubing and associated equipment, such as by the placement of sand ice screens, filters, liners and so forth. These prior attempts have been unsuccessful for a number of reasons among which is that these mechanical devices fail to prevent completely the flow of the formation particles into the production equipment. In addition these devices interfere with various types of completion and workover operations. In recent years, the industry has attempted to avoid the difficulties encountered in the use of mechanical devices by employing various chemical compositions to effect consolidation of the underground incompetent formations. These methods have generally consisted of injecting into the underground formation polymerizable resinous materials which when subsequently polymerized form permeable barriers in the formation to prevent the sand particles from movement therethrough. However, this technique of sand consolidation has not met with wide-spread acceptance because of the inherent difficulties of elfecting polymerization of the resinous materials in the formation to a degree sufiicient to consolidate these underground formations and yet permitting the unobstructed flow of the desirable formation fluids therethrough. Further, the cost associated with these resin coating methods has been relatively high in comparison with the prior mechanical methods.

By the method of the present invention one is able to treat effectively the underground formation to be stabilized in a rapid and efficient manner while avoiding the disadvantages of these prior art methods both mechanical and chemical.

One object of the present invention is to provide an improved method of treating underground sand containing formations to stabilize the incompetent formation. An additional object is to provide a fluid permeable barrier between the formation sand and the well bore to prevent or to minimize the flow of unconsolidated sand particles therethrough while maximizing the flow of desired fluids and particularly petroleum hydrocarbons therethrough. A still further object is to provide a novel treating composition for use in stabilizing incompetent sand formations and to a method of placing same to form a permeable cement filter against the incompetent formation.

How these and other objects of the invention are accomplished will become apparent with reference to the accompanying disclosure. In at least one embodiment of the method of this invention at least one of the foregoing objects will be obtained.

It has now been discovered that an improved method of treating an incompetent sand containing underground formation comprises introducing against said formation a particular treating composition consisting essentially of a hydrocarbon oil wet sand and cement admixture [slurry] dispersed or suspended in an aqueous carrier medium in an amount sufficient to stabilize the formation and then to contact the introduced [slurry] treating composition with an aqueous solution of a hydrophilic surfactant to penetrate the oil layer about the sand and cement components of the [slurry] treating composition and to effect setting of the cement to form a fluid permeable barrier [film] between the formation and the well bore. The resultant formed permeable cement barrier serves to prevent or to materially reduce the flow of the unconsolidated sandy particles therethrough while permitting the flow of desirable formation fluids through the permeable barrier at a substantially unimpaired rate.

In carrying out the method of the present invention the [permeable cement slurry] treating composition suspended in the aqueous carrier medium is pumped down the well bore under suflicient pressure to force the hydro carbon oil wetted sand-cement [slurry] admixture against the unconsolidated formation adjacent to or in reasonable proximity to the well bore. When the [permeable cement slurry] treating composition is placed against the formation to be consolidated the [slurry] treating composition then is contacted with an aqueous solution of a hydrophilic surfactant which displaces the oil layer around the sand-cement particles and renders these particles water wet. The cement component of the [slurry] treating composition then sets up and hardens. After the cement hardens the well can be equipped for production and the formation fluids can be recovered by passing through the resulting formed permeable cement barrier into the well bore and recovered therefrom without the formation fluids being contaminated with the presence therein of unconsolidated sand particles.

The method of the present invention is particularly adaptable for use in any type of well completion but is generally used in a well wherein casing has been set and which has perforations therein at the desired intervals behind which the unconsolidated formation sands are located. Packers can be initially set above and below the perforated intervals to prevent the [permeable cement slurry] treating composition from passing into the nonisolated portions of the well and also to permit build-up of sufficient pressures on the [slurry] treating composition to force same through the perforations and against the formation without plugging up the well bore. After the [permeable cement slurry] treating composition has been forced through the casing perforations and against the formation and after it has been contacted with the aqueous solution of the hydrophilic surfactant the well is closed in to permit the cement to set and form the permeable cement barrier for the unconsolidated sand in the formation.

The [slurry] treating composition useful in the method of the present invention must meet certain specific requirements. The sand component in general should be closely sized in the broad range 12-80 mesh, i.e.: 12-20, 20-40, 40-60 or intermediate meshes, to permit effective relatively high permeability cement barriers being formed. In addition, the ratio of the sand component to the cement component prior to the sand and cement being wetted by the hydrocarbon oil component of the [slurry] treating composition should be about 3 parts to about l2 parts by weight of sand per part of cement. It has been found that a frac sand, i.e. a sand customarily used in formation fracturing operations, having a size of between about 20 and 40 mesh is most suitable for use in the [cement slurry] treating composition of the present invention. It is preferred to use a graded sand with the larger grains being not more than about twice the diameter of the smaller grains, i.e. 12-20 mesh, 20-40 mesh, 40-60 mesh, etc. In general, a 20-40 mesh sand is used because of its ready availability and adaptability for use in stabilizing most formations. In addition, the use of a 20-40 mesh sand appears to prevent premature bridging which is likely to be more prevalent with finer mesh sands. Sand particles which are coarser than about 12 mesh and finer than about 80 mesh are unsuitable for use in the composition of the present invention. The coarser particles are not satisfactory because the resultant set cement barrier has too great a permeability to prevent the flow of very fine unconsolidated sand particles therethrough when the well is placed on production. Very fine sand particles, that is those sand particles finer than about 80 mesh, are unsuitable because the resultant set cement has too low a permeability to permit the flow of desired formation fluids therethrough.

The cement component of the composition of the present invention should be present in the dry mixture in a ratio of about 1 part of cement to from 3 to about 12 parts by weight of sand, on a weight basis. The cement component of the composition of the present invention may be any of the cements normally used in oil well cementing operations as well as plaster of Paris cement. It is preferred that the cement component be a light weight portland cement having a density of about pounds per cubic foot and a chemical analysis approximately as follows: silicon dioxide 38.3%, aluminum oxide 13.0%, ferric oxide 5.2%, calcium oxide 35.7% magnesium oxide 1.6% and sulfur trioxide 2.4%, with a loss on ignition of approximately 3.3%. This particular light weight portland cement has been found to be most suitable in the composition of the present invention since permeable cements made from this cement are most stable to attack by formation brines containing sodium chloride or sodium sulfate. Other oil well cements are not as resistant to attack by formation brines or sulfate solutions and therefore are not as practical for use in the cement composition of the present invention. These other cements appear to lose some of their compressive strength and become eroded from contact with sodium chloride and sodium sulfate solutions. In contrast the cements of the composition of the present invention are very resistant to erosion by sodium chloride or sodium sulfate solutions and do not lose their compressive strengths even after prolonged exposure thereto.

The hydrocarbon oil component of the [slurry] treating composition should be employed in an amount of from about 0.4 part to about 0.8 part by Weight per part by weight of cement. It is preferred that the oil component be employed in an amount of about 0.5 to about 0.6 part by Weight per part by weight of cement. Use of the oil component in this amount provides sulficient oil to wet the cement and sand components of the [slurry] treating composition and at the same time avoids an excess thereof which could possibly damage the unconsolidated underground formation when the [slurry] treating composition is placed adjacent thereto.

Suitable hydrocarbon oils include the kerosene and diesel oil fractions of a petroleum crude oil.

A necessary component of the petroleum oil fraction of the composition of the present invention is an oil wetting water repellent agent, i.e. a water insoluble oleophilic non-ionic material of relatively high molecular weight which will permit the petroleum fraction to oil wet the surfaces of the sand and cement particles in the [oil slurry] treating composition. The oil wetting agent must contain an oleophilic group and a polar group for preferential adsorption on or at the oil and sand-cement interfaces. Representative oil wetting agents useful in the practice of the present invention include the relatively high molecular weight amines such as for example, the C -C hydrocarbylamines, decyl-, dodecyland octadecylamine, the C C fatty alcohols such as cetyl and octadecyl alcohol, the C -C alkylated phenols and naphthols, natural fatty materials such as lanolin, lard, cottonseed oil and fatty acid glycerides, amides such as the C12-C13 fatty acid amides, and mixtures of these oil wetting agents.

The oil wetting agent is used in an amount of from about 1 to about 10% by weight, based on the weight of the cement particles in the [slurry] treating composition.

The aqueous carrier medium containing the suspended oil wet sand and cement solids is pumped down the well bore and into the formation to be consolidated at a rate of from about 1 to 4 barrels of the suspended solids in the carrier medium per minute. Such pumping rates have been found to give the most satisfactory results in the practice of the invention.

An aqueous surface active agent solution contacts the emplaced oil wetted sand-cement particles to displace the oil therefrom and to initiate hardening of the cement. The surface active agent used must be a water soluble material to penetrate the oil-sand-cement interface and water wet the cement particles and remove the oil therefrom. Representative surface active agents that will perform satisfactorily in the present invention include anionic, cationic and nonionic materials such as the alkyl, aryl or alkal'yl sulfates and sulfonales, the sulfated and sulfonatcd alkyloxylated amides, esters or ethers, hydrocarbylamine salts, esters or ether-esters of natural fats and oils, or alkyl phenols. The surface active agents include polyoxy-ethylene sorbitan-monolaurate, monopalmitate and -monooleate, oxyalkylated arnyl phenol, alkaryl polyether alcohols and polyoxyethylene ether. A preferred surface active agent is an ethoxylated nonylphenol containing about 9.5 moles of ethylene oxide, known by the trade name Surfonic N-95.

Example I A mixture of 700 grams by weight of a frac sand known by the trade name Ottawa having a particle size of 2040 mesh and 140 grams of a hydraulic cement known by the trade name Trinity Lite Wate Cement was prepared by intimately mixing the sand and cement. There were added to the mixture with stirring 100 ml. of a kerosene fraction containing 10% by volume of dodecylamine. The resulting stirred [mixture] treating composition of oil wet solids was suspended in about 2500 ml. of water. The suspension of oil wet solids in the aqueous carrier was pumped at a pressure of 10-50 p.s.i.g. into a test cell measuring 3 inches in diameter by 6 inches in length. The cell was about half filled with packed sand particles having a mesh size of 70-300. The oil wet sand-cement [mixture] treating composition was filtered out of the aqueous carrier liquid. Thereafter the sand pack was treated with 500 ml. of a water solution containing ml. of an ethoxylated nonylphenol having an average of 9.5 ethylene oxide groups surface active agent known by the trade name Surfonic N-95. The surface active agent in the water displaced the oil from the sand-cement particles in the pack and hydrated the cement. A hardened cement resulted after a 24 hour Waiting-on cement period. The water permeability of the hardened cement was found to be about 7 darcies ivhich was sufiicient to block the flow of very fine sand particles therethrough.

Example II 1400 g. of a 20-40 mesh frac sand were mixed with 255 g. of a hydraulic cement known by the trade name Trinity Lite Wate Cement. 300 g. of the sand/cement mixture were then mixed with 22 cc. of a 10% solution of dodecylamine in a commercial motor oil having a viscosity index of 75 and an API Gravity of 24. The oil is a blend of a refined paralfin base distillate and residual fractions and contained minor amounts of conventional lubricating motor oil additive such as a pour depressant, a detergent, anti-oxidant, etc. The oil wet solids were then placed in a large container and covered with about 2 liters of fresh water. A pump was then used to pick up [a mixture of] the oil wet solids and water carrier liquid and force [this mixture] same into a 3" x 6" test cell that had been previously partly filled with 70-170 mesh sand. The oil wet solids filtered out against the sand in the cell while the water passed through. After the cell was packed with oil wet solids, the water present in the cell was displaced with 400 cc. of a 1% aqueous solution of the wetting agent known by the tradename Surfonic [M] N-95. The surfactant saturated cell was then placed in a water bath at l40-l60 F. and allowed to set overnight. The next day a water flush and other tests of the cell contents showed that the oil wet materials had been converted into a solid mass of high permeability and of about 1200 p.s.i. compressive strength.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A method of treating an oil-containing incompetent formation penetrated by a well bore to prevent the movement of unconsolidated sand particles from said formation to the well bore as the oil is recovered from said formation which comprises forming a [slurry] treating composition of sand, cement and sufficient amount of a pctroleurn oil fraction containing an oil wetting agent therein to oil Wet the sand and cement particles, suspending the resulting [oil wetted sand and cement particles] treating composition in an aqueous carrier medium, injecting said formed aqueous suspension against the unconsolidated formation at a pressure suflicient to force the carrier of the aqueous suspension into the unconsolidated formation, contacting the [aqueous suspension]placing treating composition with an aqueous surface active agent solution to water wet the cement particles, permitting the cement to set to form a permeable cement, and recovering oil from said formation through the formed permeable cement.

2. A method as claimed in claim 1 wherein the [slurry] treating composition contains from 1 to 10% by weight of a water insoluble, oleophilic nonionic material of relatively high molecular weight based on the weight of the cement particles.

3. A method as claimed in claim 2 wherein said oil wetting agent is a member selected from the group consisting of a C -C aliphatic-amine, -alcohol, -acid, -arnide, -glyceride, a C -C alkyl phenol, a C -C alkyl naphthol, lard, lanolin, cottonseed oil and mixtures of these materials.

4. A method as claimed in claim 2 wherein said oil wetting agent is a hydrocarbyl amine containing 12-18 carbon atoms.

5. A method as claimed in claim 4 wherein said [primary] amine is dodecylamine.

6. A method as claimed in claim 1 wherein said surface active agent is an ethoxylated nonylphenol containing an average of about 9.5 ethylene oxide groups.

7. A method as claimed in claim 1 wherein the [slurry] treating composition consists essentially of cement, from 3 to 12 parts by weight of sand particles having a mesh size of from about 20 mesh to about mesh, from about 0.01 to about 0.10 part by weight of an oil wetting agent and from 0.40 to 0.80 part by weight of a petroleum oil fraction, each per part by weight of cement [particle].

8. A method as claimed in claim 1 wherein the [slurry] treating composition is suspended in the aqueous carrier medium in an amount of from about 1 to 5 pounds of the [slurry] treating composition per gallon of the carrier medium.

9. A method as claimed in claim 1 wherein the petroleum oil fraction is a kerosene fraction.

10. A method as claimed in claim 1 wherein the petroleum fraction is a diesel oil fraction.

11. A method as claimed in claim 1 wherein the unconsolidated formation is washed with a salt water fraction to remove at least a portion of the unconsolidated sand particles adjacent to the well bore and to form a cavity in said unconsolidated formation prior to injection of the aqueous suspension of the [oil wetted sandcement particles] treating composition against said formation.

12. A [sand-cement slurry] treating composition suspended in an aqueous medium fraction for use in forming a permeable cement barrier [film] in a sand-containing, unconsolidated-oil producing formation which comprises cement, from about 3 to about 12 parts by weight of sand particles having an average mesh size of from about 20 mesh to about 80 mesh, from 0.01 to about 0.10 part by weight of an oil Wetting agent, and from 0.40 to 0.80 part by weight of a petroleum oil fraction, each per part by weight of cement, said [slurry] suspended treating composition being present in an amount of from about 1 to 5 pounds per gallon of the aqueous medium.

13. A treating composition as claimed in claim 12 wherein the petroleum oil fraction is present in an amount of from about 0.5 to 0.6 port by weight, per part by weight of cement.

14. A treating composition for use in forming a permeable cement barrier in an unconsolidated sand-containing formation which comprises cement, from about 3 to about 12 parts by weight of sand particles having an average mesh size of from about 20 mesh to about 80 mesh, from 0.01 to about 0.10 part by weight of an oil wetting agent, and from 0.40 to 0.80 part by weight of a petroleum oil fraction, each per part by weight of cement.

15. A treating composition as claimed in claim 14 wherein the oil wetting agent is a hydrocarbyl amine containing from 12 to 18 carbon atoms.

16. A treating composition as claimed in claim 15 wherein said oil wetting agent is dodecyl mine.

17. A method of treating an incompetent formation penetrated by a well bore to prevent the movement of unconsolidated sand particles from said incompetent formation to the well bore as formation fluids are recovered from said formation which comprises forming an aqueous suspension of a treating composition consisting essentially of cement, sand having a particle size between 10 and 80 mesh, and a sufficient amount of a petroleum oil fraction containing an oil wetting agent therein to oil wet the sand and cement particles, placing the aqueous suspension of said treating composition against the uncolia'ated formation, contacting the placed treating composition with an aqueous surface active agent solution to water wet the cement, permitting the cement to set to form a permeable cement barrier between the formation and the well bore whereby formation fluids can be recovered by passage through the formed permeable cement barrier.

18. A method as claimed in claim 17 wherein the aqueous suspension of the treating composition is placed against said formation by injecting said suspension at a pressure sufficient to force the aqueous suspension against the unconsolidated formation.

19. A method as claimed in claim 17 wherein the treating composition consists essentially of cement, from 3 to 12 parts by weight of sand particl s having a mesh size of from about 10 mesh to about mesh per part by weight of cement and wherein the size of the largest grains is not more than about twice the diameter of the smallest grains, from about 0.01 to 0.10 part by weight of an oil wetting agent, and wherein the amount of the petroleum oil fraction present in said treating composition is from about 0.40 to 0.80 part by weight per part by weight of cement.

20. A method as claim in claim 17 wherein the treating composition is suspended in the aqueous carrier medium in an amount of from about I to 5 pounds of the treating composition per gallon of the aqueous carrier medium.

21. A method as claimed in claim 17 wherein the petroleum oil fraction is a kerosene fraction.

22. A method as claim d in claim 17 wherein the petroleum oil fraction is a diesel oil fraction.

References Cited The following references, cited by the Examiner, are of record in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,285,302 6/1942 Patterson 166-276 2,798,003 7/1957 Morgan et a1. 10690 2,800,963 7/1957 Roberts et a1 106-90 X 2,840,483 6/ 1958 Morgan et a1. 106-90 X 2,842,449 7/1958 Bearden et a1. 10690 3,079,268 2/1963 Brooks 10698 3,119,448 1/1964 Rhoades 166-276 X 3,145,774 8/1964 Patchen 10690 X 3,242,986 3/1966 Hower 10690 X 3,244,229 4/ 1966 Hujsak et a1. 1 166-276 STEPHEN I. NOVOSAD, Primary Examiner US. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. RE 27,271 Dated January 97 Bobby G. Harnsberger 8: Joy '1. Paton It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

F001. 5, line 2 Place a. dash before monopalmitate.

Col. 6, line 9 Change "placing" to --placed-- Signed and sealed this 11th day of July 1972.

SEMI, Att es t EDWARD M. FLET CH Eli, JR Attes ting Offic er ROBERT GOTTSCIh'LLK Commissioner of Patents 

